Differential in vivo Aminoacylation and Utilization of Homologous Species of E. coli Transfer RNA

Some recent observations have indicated that activation and transfer of an amino acid to its cognate tRNA is involved not only in general protein synthesis but also in regulatory phenomena of cellular control (Fangman and Neidhardt, 1964; Eidlic and Neidhardt, 1965; Roth et al. this volume). Since more than one chemically resolvable species of tRNA corresponds to many of the twenty standard amino acids, and since some of the homologous tRNA species cognate to the same amino acid are known to respond to different synonymous codons representing that amino acid, it seems possible that the multiplicity of homologous tRNA species reflects a differentiation in their role in regulatory processes. In order to examine this possibility, we have analyzed the relative degree of aminoacylation of various homologous tRNA species isolated from bacteria under different physiological conditions of growth, and determined the relative frequency with which homologous tRNA species are used in...